The following diagram is a system to form an aerial 3D image but i don't know what name it is. I can understand why the image can be 3D but I don't know why it can be observed without screen. At the place where I saw that gave it a name "Reflective hologram". However, in holography theory, the "3 dimensional imgae formation" is just on a single surface film. The "3D image" that we observing is just a combination by lot of layers. It's not like the following, this is real 3D image.

Thank you for your siteI can understand the ray diagram and why the image can be 3D but I don't understand why the image can be observed without screen. When we form a real image just by convex lens or concave mirror, the image can't be observed, unless we sit on the image point. At least, we won't see something aerial like this toy.

For the java, I have some confusions, when the distance between mirror and the object is 0, the image should be formed on the focus. For the red line, do the different ray paths exsist?If the ray paths like the java showing, when there is not the upper mirror, the rays go away, so how can the image be formed at focus??

There is on thing I can sure, the total image must be formed by lot of views of images. thus it is a combination of mutliimage. From this, I made an assumption that when mor than 1 image are overlapping, we may observe it without screen. Is that possible??

I have made an assumption that is because of interference of muti-foucsing point but my lecturer said that is not true, I have no idea, no direction to analysis that now.............

The only way we can see something is that light must be able to enter our eye. And our mind will try to interpreted where is the image. The above two light paths you shown will not be able to enter our eye at the same time. Althought there can be many light paths emitted from the object. Only those paths which will be able to enter our eye can be used to interpreted where the object is. The light paths shown on the original documents will not be able to enter to your eye at the same time, so I create the simulation to show how the image could be formed. The red and blue light paths represents light emitted from two different points of the object. When those light enter our eye , our mind interpreted it is coming from the top of the mirage.

Thank you very much!!!!!!!!!!!When I'm studying this case I even forgot the most most basic knowledge..........................

"The only way we can see something is that light must be able to enter our eye. And our mind will try to interpreted where is the image. "

Let me conclude somthingWe can see the image without screen in this case because the system reflect light rays in almost all directions then enter our eyes. For the other case(e.g real image by concave mirror/convex lens) light rays are going in the same direction, in the condition that screen is absent, we can't see the image unless we sit on the area that dirtributing light rays or the image point.

Right??

One more question, we're going to apply this technique on projector to form a real 3D image but it seems to be somebody done that already http://www.io2technology.com/indexhttp://www.fogscreen.com/Although those products are projecting 2D aerial image, I think the theory used in those products are close to my case. We must make our project faster..................

Yes. Light need to enter our eye for us to see any object. Normally, we do not see the path of ray when we use a laser pointer. The light path shown in the movie(e.g. Star War) for laser rays are not real, especially in the space. Nothing can reflect those light.

The sun is always shining even in the evening. But we did not see the sun light at night because those light go away from us. Only when some of those light hit ths surface of moon and reflected back to our eys so that we can see the moon. :-)